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What method does ATC use to calculate distance between two aircraft?
The distance between aircraft must be larger than the minimum separation all the time and is therefore quite important for Air Traffic Control (ATC). As I need to calculate the distance between aircraft for my research, I'm wondering if there are any regulations (in Europe) about how exactly the distance is determined.
How exactly does ATC determine the distance between two aircraft?
I suppose that they are working with latitudinal and longitudinal coordinates and probably the altitude to determine great circle distances. To get the coordinates, they could use either radar or the position which is communicated by the aircraft.
The task to calculate the distance from coordinates is not that trivial as it may sound from the first impression. One method to calculate the distance is the haversine formula. In all methods, the assumed earth radius is rather crucial. If the distance is calculated in that manner:

Which value is used as the earth radius?
Are the different earth radii from the equator to the meridian regarded?
Is the altitude of flights included in the calculation?

Using a range/azimuth calculation from radar returns would probably be a lot simpler than doing it from coordinates.  I don't think they are looking for precision beyond ~25 feet or so.

@JoelM.: You are overestimating the precision. The radar target on the scope is about a mile wide in the scale of the scope (for radars monitoring en-route traffic).

Does ATC radar provide any data other than the scope display?  I would expect that the system has better range resolution than one mile.

The things you mention would matter, if you wanted to know the distance to 6 or more significant digits. But ATC does not need that precision. They need to be able to tell whether it's 4 nmi (too close), 5 nmi (still sufficient, but getting in trouble) or 10 nmi (no worry, but should not be heading directly towards each other). That is one significant digit.
The controller does not use any formula. They just look at the distance of the targets on the radar scope (which is drawn properly to scale). And possibly use the grid that is drawn over it or compares to the leader lines (indicating velocity) or history trail. The controller doesn't need precision, they need to look and see. And they are not getting any precision; on centre station (controller handling en-route traffic) the radar target blob is about a mile wide.
Until recently, aircraft did not broadcast position at all. Many still don't; not all aircraft are equipped with ADS-B. For those that don't, the interrogator may have precision similar to DME (~ 0.1 nmi) in range and a degree or two in angle. Not great precision either. The radar also has single rotating antena that takes couple of seconds to scan the whole circle, so the position of the aircraft is only updated once every few seconds. Jet airliner in cruise moves some 700 m in 3 s.
On such radar, the scope most likely transforms directly from the angle and distance reported by the radar to the screen coordinates. Altitude was usually not taken into account (so higher targets appear further than they really are!) in the older systems.
New radars with ADS-B support (less busy areas don't need it) need to combine the radar data with coordinates reported by ADS-B, which are in WGS84, so WGS84 is usually used as intermediate format for the collected data. But shortcuts can still be taken in the software.
I don't know what which radar system manufacturer uses, but I work on navigations and we tested the precision. By assuming Earth is flat and the coordinate system is orthogonal and using simple Pythagorean formula, you can still get 3-4 significant digits (unless you are working around north or south pole) for points tens of miles apart, which is more than enough for the radar screen. So the system can simply multiply longitude and latitude with appropriate factors (that depend on latitude of the sector centre) and get sufficient precision.

The shortcut is usually map it to a distance equivalent (or near enough) projection centered on the airspace and then hypot(dx, dy)

@ratchetfreak: Yes, that's the one I mentioned.

Radar systems don't report in WGS84, they report in azimuth and range. The downstream processing system does the conversion into WGS84 and combines data of multiple surveillance systems into single tracks for each aircraft. The display is often in stereographic projection. The display software incorporates features such as grids and rulers to measure exact distance if needed (e.g. distance to navaid), but eye-balling should be sufficient for spacing.

@DeltaLima: I never said Radar systems would report in WGS84. I mentioned it for when adding ADS-B data. I reworded it a bit to make it clear it only applies to those data.

I just wanted to clarify that the introduction of ADS-B does not impose new requirements on new or old radar systems. The multisensor tracker will convert the radar data to WGS84 (it already did that before the introduction ADS-B in most cases). An update to the tracking software is needed to fuse the ADS-B data into the radar tracks, but that part is independent of the existing radar systems.

Another note: the approach/terminal radar systems I've seen have "helpers" for the controllers which may be configurable, like position trails for speed, heading indication (with a distance), and even a cursor to measure distance between targets and the estimated point of conflict.
Also, definitely agree with the answer's comment that assuming orthogonal coordinates works great for this scale, so long as the limitations are understood.

"They need to be able to tell whether it's 4 nm (too close)" I've always hated seeing the symbol for nautical miles without capitalisation until today.

@dougk_ff7 These are called "history dots / trail" and "leader line" (usually set to 5nm, 3nm or 1min, controller's preference).
+1 or using nmi instead nm. ;)

@SentryRaven Yeah, you're correct -- thanks for the added info!


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Is it enough for crossing/ascending/descending IFR-flights to adhere to the separation minima?
The separation minima in Europe are in general 5NM lateral or 1000ft vertical. If the safety distance is too small, there is a conflict (loss of separation). When both aircraft are on the same track, the adherance to the minimal separation is relatively easy. But if two trajectories cross the same point horizontally, for example over a beacon, the adherance to the separation minima seems not that easy anymore. The same is true for ascending or descending flights which burst through different flight levels.
Is the adherence to the separation minima for IFR flights enough to avoid airborne conflicts for crossing/ascending/descending flights, too?
If not, what is the minimum distance between two flights in space and time, that precludes all the different possible conflict types [page5]? For example there are local conflicts, which occur, when two aircrafts cross a given point from different directions in under 4 minutes.
This questions refers to the european airspace at best. See the linked question How much is the minimum safe distance between two planes in-flight?

I'm not sure I understand your question. If you always ahere to the separation minima in all phases of flight then there can't be a conflict (ignoring the issue of VFR traffic). And why would it be difficult to keep separation when flights cross the same waypoint? That's what the vertical separation limit is for. I'm probably misunderstanding your question, but it would be great if you could clarify it a bit more.

The separation is 5 miles, independent of directions. But then I don't really understand what the local conflict definition is even about. And on the other hand TCAS may give RA at more than 5 miles (about 9, in fact) if the aircraft are heading in opposite directions, because it is defined by time (40s).

I am confused about the question as well. If the question boils down to: Is applying IFR separation enough to avoid airborne conflicts, then the answer is: Yes. That is what IFR separation is intended for... Can you rephrase your question, maybe into simpler terms or clarify what you are asking?

Maybe I really overcomplicated the question - Ok, IFR separation is enough to avoid airborne conflicts. I was just confused by the conflict types. And by the local conflict, which is mentioned at Wikipedia.
I think keeping separation when two flights cross each other is more different, because small deviations lead to very big changes in the time when the trajectories cross. (For example a small deviation in heading angle of one flight in the direction from which the other flight comes.)

You need to keep in mind that separation is 5nm OR 1,000ft, not AND. ATC is trained to apply either of the two or both, even when giving flight level/altitude changes or headings.

I've checked the references above and I have not heard about local conflicts yet that have to do with 4min timing over fixes. It doesn't make a lot of sense either, as depending on speed, the distance between two aircraft crossing a fix 4min separated can be different. A slow moving aircraft behind a faster aircraft would be farther away over the same fix than two aircraft with similar speed. The levels of conflict from the other document seems very theoretical and rather for analysis than daily use. A conflict is a conflict and you have separation to avoid conflicts :)

The only reference I have to the number 4 being used is when dealing with wake turbulence separation and when sequencing aircraft with weight category heavy behind another heavy. The unit used there however is always nautical miles, not minutes. Using minutes at varying speeds is not an accurate means to ensure separation...

I don't understand what you are asking. Your references are a scientific paper and wikipedia. While they may seem reliable to you, they are not the sources from which Air Traffic Control is defined. Please look at ICAO PANS ATM (Doc 4444) to get an idea of how separation is provided.

@DeltaLima actually I did have a look - the document is somewhat hard to parse for me. And AFAIK there may be some other definitions from Eurocontrol and the European nation states which overrule some aspects of the ICAO PANS ATM... I will have a more rigorous look at that document though.

My rather longish answer has been undeleted, if you want to check it out. :)

In the ICAO PANS ATM (Doc 4444) (*) the vertical separation is specified as 1000ft (or 2000ft):

5.3.2 Vertical separation minimum
The vertical separation minimum (VSM) shall be:
a) a nominal 300 m (1000 ft) below FL 290 and a nominal 600 m (2000 ft) at or above this level, except as provided for in b) below; and
b) within designated airspace, subject to a regional air navigation agreement: a nominal > 300 m (1000 ft) below FL 410 or a higher level where so prescribed for use under > specified conditions, and a nominal 600 m (2000 ft) at or above this level.

The minimum horizontal separation mimumum is 5 NM for flights under radar control:

8.7.3 Separation minima based on ATS surveillance systems
8.7.3.1 Unless otherwise prescribed in accordance with 8.7.3.2, 8.7.3.3 or 8.7.3.4, or  chapter 6 (with respect to independent and dependent parallel approaches), the horizontal separation minimum based on radar and/or ADS-B and/or MLAT systems shall be 9.3 km (5.0 NM).

The approach and departure phases of flight has some small deviations, e.g. small aircraft behind heavy aircraft have to keep 6 NM horizontal separation because of wake vortexes.
(*) Unfortunately I couldn't find the official Doc 4444 on the ICAO website.

Doc 4444 is a document that you need to buy from ICAO. For $350 you can download it from their website.

Good to know, thank you!

In Europe the standard minimum radar separation is 5 NM en-route.  In many Terminal Manoeuvring Areas, it is 3 NM. On final approach it can be 2.5NM or even less when on approach to parallel runways. Of course this increases the requirements on the surveillance systems (higher accuracy, integrity, update rate and probability of detection).

This might not be the answer to your question, but maybe it will help you understand separation.
Your question specifically asks for how separation is ensured between climbing, descending and crossing traffic over navigational fixes (NAVAIDs).
Flight routes are planned for traffic to use certain flight levels en-route, which follow the semicircular/hemispherical rule in effect in that country or are bound to the airway being used. In my example picture below I will use the German semicircular rule of eastbound flights using odd flightlevels.
(Image Source: Own Work - Program used: Aircraft Situation Editor (ASE))
Both aircraft will cross the HMM VOR roughly at the same time, based on the ground speed displayed. The westbound aircraft (DLH123) is at FL200 (even FL), the eastbound aircraft (BER456) is at FL210 (odd FL). The separation between both aircraft overhead HMM VOR will reduce to 0nm lateral separation, but 1.000ft of vertical separation, and thus, the separation criteria are met.
(Image Source: Own Work - Program used: Aircraft Situation Editor (ASE))
In this example, I need BER456 to descend to FL100, but I have crossing traffic from the right which would cause a cleared conflict, if I issue a descent clearance directly to FL100 without any conditional instructions. I can use a bit of mathematics here to ensure separation however and issue a clearance nevertheless.
Both aircraft are travelling at 420kt GS. An aircraft will also descend 1.000ft in 3nm, rule of thumb from every flight instruction book available. To ensure 5nm of lateral separation, I would need a buffer of 2.000ft during descent to the crossing traffic, not factoring in that the other traffic will be on a divergent track anyway. Let's just measure the distance to the HMM for simplicity.
My instruction to BER456 would be:

R: BER456, when ready descend FL100, cross HMM VOR at FL230 or above (rate of descend 2.000ft/min or less)

With this instruction, I can issue a clearance to BER456 that will allow the aircraft a continuous descent to FL100, while ensuring minimum separation is kept to the other traffic. Overhead HMM VOR, both aircraft will have 3.000ft of separation. After BER456 has descended a further 2.000ft, it will have 6nm and 1.000ft of separation, making it well clear of a conflict, especially since the traffic is divergent.
The dirty solution would have been to clear BER456 to FL210 and after 5nm issue another clearance to FL100, but this doubles the frequency time and also interrupts the descent for BER456.

Thank you for this answer and the insight into the conditional clearance! Unfortunately, I can't upvote anybody yet. To be a bit more unspecific, I assume separation between climbing, descending and crossing traffic aside from NAVAIDs has to be guaranteed, too? In your example, BER456 crosses other flight levels too and there could be - theoretically - some more traffic...

@JaBe In general, the separation minima need to be maintained, using NAVAIDs is just a tool. There is one possibility for descending and climbing traffic, which depends on jurisdiction, which is during daytime, in VMC: You can transfer responsibility for separation to the pilot and have them climb or descend through another aircraft's level. This is also called visual separation in some documenation. If you cannot upvote, you can still mark as the answer to your question. ;)

I see you edited your comment: ATC uses radar to maintain separation, so when issuing descend or climb instructions, ATC needs to make sure that no traffic will be within 5nm of the descending or climbing traffic on the same level.

The separation of 5nm (Surveillance system based) or 1000ft vertical is the minimum and safe separtaion between two aircraft in any configuration. Though it needs to be understood that at least one of these separation need to be maintained at all points of time.
If there is likelihood of breach of one kind of separation in near future as in the case of converging traffic at same level, Air Traffic Control has to initiate action well in advance to ensure that other kind of separation is established before the existing separation is breached.
So the question of TCAS warning does not arise.When the process for established other mode of separation is to be initiated is the whole job of ATC.  That is what Air Traffic control is all about.

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What effects to controllability are there when the rear doors are opened on a KC-130?
Many years ago, I was part of a LRRP drop taking photos from inside a KC-130 aircraft. The rear doors are (relatively speaking) huge. The top half pivots up and into the craft, while the bottom half descends down and (I assume) into the airstream.
When the main doors are opened like that, how does that affect the stability and controllability of the airplane? Would the pilot have to trim down or up, or do nothing?
While my personal experience is that plane, I wonder of any plane that opens large portals into the airstream.

Are you specifically asking about KC-130 only or about a rear loading ramp on any airplane?

Added to question

Answer based on information found on-line. Related documentation:

USAF C-130 Operations Procedures
C-130T Flight Manual
Lockheed News Service, 1957
KC-130 Specifications
KC-130J Specifications
C-130 HALO Practices

C-130J Hercules
Source: Flight Global
The KC-130 Hercules is the tanker variant of the C-130 Hercules. The cargo opening consists of a door, and a ramp which can be operated separately.

The door is opened by rotating up and inwards the top panel.
The ramp is opened by rotating down and outwards the lower panel

Source: CQ Planes Spotting
KC-130 / C-130 have a good maneuverability at low speed.
From the the C-130 flight manual:

Door and loading ramp are operated at a speed of 150 KIAS, with flaps down at 50%.
Same conditions for flying with door and/or loading ramp open.

Low speed adjustments:

Reducing speed from 300 kt to 150 kt requires nose up trimming.
The center of gravity may be adjusted by ballasting fuel in the tanks (refueling tank and aircraft tanks).

Opening the ramp will change the aerodynamic shape of the aircraft:

The ramp will not be moved past the horizontal position (only need for full down position is to load cargo on the ground).
Moves the nose down.
Balanced by some trim accordingly.

If loads are dropped (pallets, paratroopers) or fuel is delivered, the center of gravity will roll back, with a significant nose-down tendency, and trimming will be required.
Opening the door will be less of an issue as seen on the image below:

The aircraft is near level.

Above: KC-130J Hercules (source: Military.com).
Note that the attitude is not so far from level, in spite the door is open.

Isn't the door closed in that picture?

@Jamiec: I don't think so. The door seems to be open, and the ramp closed (up) at the same time. This is the configuration seen on this video, at time mark 6:29. Must be confirmed by an someone familiar with this aircraft.

When opening the ramp, the attitude is still the same—near level. It just changes the trim, so the stabilizer has to be adjusted accordingly.

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Do non-towered airports commonly have ILS?
Is it common, uncommon or rare for a non-towered airport to have ILS (Instrument Landing System) runways? Can a non-towered airport have ILS?

Nontowered airports absolutely can have ILS approaches, and it's fairly common, though of course not as common as at towered fields.
Two examples in my neck of the woods are KIKK (Kankakee, IL) and KMTO (Mattoon, IL).
Also, at many towered airports, the tower is not 24/7 and closes at night. If such an airport has an ILS, it's still available after the tower closes; ATC services for IFR approaches are provided by a nearby/higher facility like a TRACON or ARTCC, just like a nontowered field. Two examples of this in my neck of the woods are KCMI (Champaign, IL) and KBMI (Bloomington, IL).
I am not, however, aware of any Cat II or III ILS approaches at nontowered fields.
Protecting ILS Critical Areas is usually the responsibility of the tower, but even VFR aircraft are prohibited from entering the ILS Critical Area when the tower is closed:

(1) Localizer Critical Area. Except for aircraft that land, exit a
  runway, depart, or execute a missed approach, vehicles and aircraft
  are not authorized in or over the critical area when an arriving
  aircraft is inside the outer marker (OM) or the fix used in lieu of
  the OM. AIM 1-1-9(k)

I doubt you'll find Cat II or III minimums approved at non-towered airports.  A requirement for these (among others) is that the ILS critical area be protected during these ops, and without local control there is no way to guarantee protection.


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How do airlines pay air crews for an aborted flight, in general?
I was watching this SWISS video. It's a flight from Zurich to Shanghai. Shortly after take off they have high engine oil temp in engine 3 and end up shutting it down. They declare a pan-pan-pan, dump fuel and return to Zurich. It's pretty uneventful, engine shut down aside.
Now, as I understand it, an air crew's pay begins upon push-back, and ends at gate arrival. At the very end the PIC states that for the passengers, SWISS has another plane which will be departing in two hours, but with a new crew. Assuming this crew gets no other flights for the day, did they just get only 1 - 1.5 hours pay for the day?
NOTE: even though this is a SWISS flight, I am not concentrating on that one airline. I'm curious if there are general rules for flight pay that all/most airlines follow.

How the Swiss pilots got paid would, of course, depend on Swiss policy. I suspect pay policies vary greatly between airlines and countries, but for what it's worth below are the pay policies for the four airlines I worked for in the 1980s and 1990s. At all four I would have been credited with only the time from push back until the parking brake was set on return insofar as flight time was concerned, but as you will see that wouldn't have made any significant difference in my pay.
commuter #1 no union -- a straight salary but with an hourly addition if your flight time went over a minimum, which it never did.
commuter #2 no union -- a straight salary regardless of the number of hours flown, but they never abused that.
747 freight carrier no union -- a straight salary plus an hourly addition if your flight time went over a minimum, which it occasionally did.
747 passenger carrier in-house union -- flight time hourly pay with a guaranteed minimum. You always went substantially over the minimum. They tried to get you as close as possible to the regulatory max of 1000 hours a year. Additionally, they had a policy that whenever your duty time (as opposed to flight time) went over 16 consecutive hours, you got paid for each hour over that at a rate of 1.5 times your regular hourly flight time rate. Also, you were paid half your regular hourly flight rate while deadheading. Then, if you had less than 8 hours (I might not be remembering that number correctly) between assignments, your duty time continued. My first assignment for this airline was a 32-hour duty day. I operated from JFK to AMS (Amsterdam), so my duty time started at show time, 2 hours before departure. At Amsterdam 5 hours on the ground then commercialling (riding in the back on another airline) to SIN (Singapore) and then to CGK (Jakarta) positioning for a Hajj flight. Crew scheduling regularly abused pilots, but nobody complained because you were being so well paid when they did abuse you.
The breakdown for hours at the flight time rate for that trip was approximately:

7.5 hours operating time JFK-AMS

8 hours deadheading pay AMS-SIN-CGK (half of 16 hours riding in the back)

24 hours extended duty pay (32 hours duty time minus 16 hour threshold times 1.5)

So, 39.5 pay hours at the regular new first officer rate of 55 per hour = 2,172.50, which looked pretty good to me since I had come from a carrier than paid me a straight 4500 per month salary as a 747 captain.
I can't remember all the flight time/duty time details, but back then at least the international rules were much less restrictive than the domestic rules.
Also, back then it was common practice to do things like scheduling a flight for, say, 11:59 for regulatory purposes, when everyone knew it would go slightly over the 12-hour international rule of the time.
It may be worth noting here, that the mind-set of the crew, at least the cockpit crew, is totally different from that of passengers. The passenger wants to get from point A to point B, whereas the crew is simply 'at work' regardless of whether they go anyplace or not. Consequently, at least in my experience and opinion, delays aren't nearly as frustrating to crew as they are to passengers.

So for #4 you weren't being paid for duty time, just flight time, and duty time just mattered for increasing how much you made per flight hour?

@cpast I'll edit the answer to make it clearer.

A common pay scenario for US pilot unions is known as "block or better".  In the case of an aborted flight like you example, you would be credited the scheduled block time toward your monthly pay guarantee under those rules.
The specifics of any pay questions will fall under the collective bargaining agreement (union) or company policy (non-union) of the specific company involved.

Your and Terry's answers were what I was looking for. Seeing this concerned me a might, because if the pilots were going to be 'stuck' with a no pay due (or very little, due to the short duration of their aborted flight) that could play into the thought processes of the pilots, vice pure safety.

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text:
How can avionics detect tailwind?
We can see the effect of the tailwind on the plane's flight direction on the modern military fighter jet huds. I wonder about how can the avionic systems detect tailwind and which sensors using in the process.

It just has to compare it's airspeed and heading, taken from pitot and INS data to ground speed and track from GPS

In simple terms, at any given power setting and altitude a given aircraft will travel at a certain speed. Let’s say it’s 500 kts. The GPS in the aircraft can tell the groundspeed. Let’s say it’s 600kts. Then the tailwind is 100 kts. The concept is simple, but the implementation more difficult. Small aircraft pilots actually do a lot of this in their head to get rough estimates of the windspeed and direction. It is especially important when entering holding patterns and when landing with a crosswind.

It seems a complicated sensor fusion process including INS (Accelerometers, Gyros and Compasses) and GPS for ground speed and Pitot system for true air speed and compare both of the vectors. In that case we can calculate the angle of attack with similar way.

@JScarry:  It is not even a question of altitude and power setting.  Airspeed is known from the Pitot tube.  Ground speed is known from GPS.  The difference is your headwind/tailwind component.

@abelenky True airspeed goes up about 2% per 1000' above standard atmosphere, so altitude matters a bit in the calculation. But you are correct, power settings don’t matter—I’ve had too much partial panel practice lately and I have power settings on the brain.

This can be sensed by means of either an INS or GPS to determine a ground velocity and both the data from the pitot static system and a magnetometer to determine the true air velocity.  The local wind velocity is the difference between the ground velocity and the true air velocity.


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Alphanumeric flight identification in flight plan
Why do some airlines use alphanumeric callsigns in the flightplan when the flight number printed on the ticket consists of only numbers?
For example, the flight TK871 uses callsign THY4JT.

when flight delays cause a duplication of a flight number- there is a suffix added.  For example- flight 1423 DFW/OKC is also operating as OKC to DFW. Normally a turn of equipment- however, DFW/OKC delayed significantly- equipment and crew is available to operate 1423 OKC/DFW.  These 2 could be in route simultaneously- one is usually designated as a suffix- 1423J  Call sign American 1 4 2 3 Juliette

Welcome to Aviation.SE! Please read the [help] to see what makes a good question / answer. Also have a read of other answers on questions for examples of what makes a good answer. Generally well formatted answers with references do best.

The question is regarding completely changing the number from 871 to 4JT, not just adding a letter at the end.


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When must full aircraft registration be used as radio callsign?
What are the FCC or FAA regulations that require one to use their full registration as radio callsign, unless abridged by air traffic control, when using an aircraft radio for transmitting?  It seems it is becoming popular to use type of aircraft and color only for transmitting.

Note that the callsign does not necessarily have to be the registration. For general aviation it usually is, but commercial operations normally use the operator name and flight number. (“blue cessna” is never a valid callsign though).

@JanHudec "blue Cessna" is a fairly common call sign when flying the Ripon arrival into KOSH for Airventure. The caveat is ATC talks to you, pilots respond by rocking their wings. You are correct though that it wouldn't be valid to call up ATC and use it as a call sign.

The AIM discusses communications with ATC in Chapter 4.

4−2−3. Contact Procedures a. Initial Contact.
  1. The terms initial contact or initial callup means the first radio call you make to a given facility or the first call to a different
  controller or FSS specialist within a facility. Use the following
  format:
(a) Name of the facility being called; (b) Your full aircraft
  identification as filed in the flight plan or as discussed in
  paragraph 4−2−4, Aircraft Call Signs; (c) When operating on an airport
  surface, state your position. (d) The type of message to follow or
  your request if it is short; and (e) The word “Over” if required.
c. Subsequent Contacts and Responses to Callup from a Ground Facility.
  Use the same format as used for the initial contact except you should
  state your message or request with the callup in one transmission.
4−2−4. Aircraft Call Signs
  2. ATC specialists may initiate abbreviated call signs of other aircraft by using the prefix and the last three digits/letters of the
  aircraft identification after communications are established.…The pilot may use the abbreviated call sign in subsequent contacts with the ATC specialist.

When operating at a non-towered field, many pilots have begun to identify their aircraft by type and color. I’m not sure when this started, but if you listen to popular YouTube flyers like steveo1kinevo, you will notice that when they are flying into non-towered fields, they just give the aircraft type, e.g. Caravan or TBM. From a practical standpoint, it makes a lot of sense. You can’t see the numbers but you can see the type and color. And unless there are lots of white Cessnas in the pattern, it is easy to keep track of who is where. What you want to know in the pattern is where are the other planes and how fast are they going.
Type and color gives you the necessary information. For me at least, it is easier to keep track of type and color than it is to keep track of N numbers.


text:
Can a dual-engine aircraft take off with only one engine?
When a dual-engine aircraft (such as the B737, A320, A330, B777 or B787) has reached the point where it is too late to abort a take off, can it take off if one engine fails?

FYI:The Aero Commander was capable of taking off, flying and landing on a single engine while maintaining a high degree of stability. To prove this, and to enhance market recognition of the plane, in May of 1951, the Company successfully completed a flight from Oklahoma City to Washington DC loaded to full gross weight with one propeller removed from the plane. This was a first for the aviation industry and a strong demonstration of the asymmetric control and responsiveness of the Aero Commander. http://www.twincommander.com/history.html

@Terry: Granted, removing the one propeller would have given that Commander an additional advantage over merely leaving the engine off; even a feathered propeller still produces drag.

@Terry Well, that was silly. Image if that engine had failed!

@Cloud Viewed from the standpoint of the aircraft manufacturer, the flight accomplished it's purpose. As I remember, the FAA (still the CAA back then) was withholding certification over questions about the aircraft's single engine performance. After this flight, they granted certification. Also, this was the same aircraft design that was used by Bob Hoover 30 years later in his aerobatic routine which he ended by gaining a bit of altitude, shutting down both engines, doing a few aerobatic maneuvers, and landing without power, usually rolling to a stop at predefined point in front of the crowd.

@Terry Wow, is there any footage of this available?

@Cloud Google "bob hoover shrike commander engines out aerobatic routine". That brought up urls to 3 videos when I did it here a minute ago.

It is a regulatory requirement (EASA CS 25) that commercial aircraft can safely fly should one of the two engines fail at any point of the flight, including takeoff at speeds beyond $V1$. (the maximum speed at which it can still stop before the end of the runway).

Control Following Engine Failure  1 An acceptable means of showing
  compliance with CS 25.143(b)(1) is to demonstrate that it is possible
  to regain full control of the aeroplane without attaining a dangerous
  flight condition in the event of a sudden and complete failure of the
  critical engine in the following conditions:
a. At each take-off flap setting at the lowest speed recommended for
  initial steady climb with all engines operating after take-off, with –
  i. All engines, prior to the critical engine becoming inoperative, at
  maximum take-off power or thrust;  ii. All propeller controls in the
  take-off position;  iii. The landing gear retracted;  iv. The
  aeroplane in trim in the prescribed initial conditions; and
b. With wing-flaps retracted at a speed of 1.23 VSR1 with – i. All
  engines, prior to the critical engine becoming inoperative, at maximum
  continuous power or thrust;  ii. All propeller controls in the
  en-route position;  iii. The landing gear retracted;  iv. The
  aeroplane in trim in the prescribed initial conditions.

Source

For a clip of this happening just as the aircraft is rotating, take a look at this video:

A simulator video of the procedure is also available:

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Are paper charts required for flights outside the USA?
Can international flights by a US operator be performed paperless or do you need complete paper charts?

Any other detail? Plane size? Type of operation? Route?

Closely related

With virtually every major US air carrier today using EFB's, the use of paper charts in the flight deck has largely fallen to the wayside. Flight crews are still being provided with the exact same information, only now it is in digital form. Most, if not all US air carriers use navigational charts and plates published by Jeppesen. Unlike FAA NACO charts and plates, Jeppesen publishes charts for airports all across the world in a greatly standardized form. This allows information to generally remain similar across countries and helps to reduce some of the differences pilots operating international flights would otherwise face. Whether paper or digital, US based flight crews would likely receive charts from Jeppesen.
All of the EFB apps in use by airlines are designed to automatically provide pilots with current charts and plates needed for any given flight in the carrier's network, provided the area is covered in the chart subscription. Prior to operating an international flight, an airline (likely their dispatch department) will review their chart subscription package to ensure charts/plates are included to cover the routing, destination, and alternate(s) of any international flight. Any areas needed that are not currently included in their subscription would be added. Once added to the airline's subscription, the charts would then automatically populate to the EFBs issued to pilots. Pilots would then just need to make sure the new charts were downloaded and they would be good to go. Pilots would then be receiving the exact same information digitally that they would if they had been provided paper charts.
From a regulatory perspective, the FAA, EASA, and ICAO have all developed standards for EFBs and as a result pretty much all developed countries allow their use. As long as an airline has received the appropriate approvals and meets standards, the use of EFBs should be a non-issue. In the US, FAA EFB standards meet or exceed ICAO standards, and ICAO standards would likely be the minimum requirement while operating internationally. I am not currently aware of any country that disallows the use of EFBs for charts, but should such a scenario arise, then an airline could potentially be forced to use paper charts. However, the odds of that happening are slim to none.

I know of at least one Part 121 carrier that routinely flies internationally with no requirement for full paper charts, and beyond the approvals for the EFB's as a replacement for paper charts in general, I don't know of any special approval needed to go without them internationally.
We do have paper High enroute charts for international (but not domestic) airways; I can't find a reference if those are required or not (and if so, by whom: FAA, other countries, or our company).
It's always hard to prove a negative, but I suspect that if your operation is approved to go EFB-only, then that approval isn't limited to only domestic routes. There may be some country that requires everybody to have the paper charts, but I don't know who.
Overwater ops has its own rules; for that, a paper plotting chart may well be required even with EFB's for enroute & terminal reference.


text:
Why do the GS and LOC indicators blink?
So, the question is in the title. Specifically referring to this video. At around timestamp 2:10 in the video, you can see the GS and LOC indicators blink. Why does it blink?

From this copy of the flight manual for the 737:

Glide Slope Pointer and Deviation Scale
...
At low radio altitudes, with autopilot engaged, the scale turns amber
  and the pointer flashes to indicate excessive glide slope deviation.
Each pilot’s deviation alerting system self-tests upon becoming armed
  at 1500 feet radio altitude. This self-test generates a two second G/S
  deviation alerting display on each attitude indicator.

And for the localizer

Localizer Pointer and Deviation Scale
...
At low radio altitudes, with autopilot engaged, the scale turns amber
  and the pointer flashes to indicate excessive localizer deviation.
Below 1,000 feet AGL, with LNAV engaged and LOC armed, the localizer
  scale turns amber and the pointer flashes if the localizer is not
  captured.
Each pilot’s deviation alerting system self-tests upon
  becoming armed at 1500 feet radio altitude. This self-test generates a
  two second LOC deviation alerting display on each attitude indicator.

What is interesting is that the pilot seems to be right on slope and right on the localizer so I would presume it is NOT flashing as a result of excessive deviation.

Is that passing a marker beacon?

I think it's the self test as it passes 1500 ft RA.


text:
What to do if expediting your ascent or descent is impossible/unsafe?
As a pilot of a small single engine plane, what do we do if ATC instructs us to expedite our climb/descent and doing so would be impossible or unsafe (i.e. we're already at the maximum safe rate of climb/descent)?

Just say "unable".  It's an ATC problem if they are not able to deal with your max performance.

The pilot always has ultimate responsibility for the safety of the flight.

You report unable, and ATC will come up with a different plan.
To provide some context: If I ask you to expedite a vertical manoeuvre, it is probably because you are on crossing tracks with another aircraft, and I want you to pass them either above or below. This could be to meet certain level restrictions, or simply because I want to provide you with continuous climb/descend as a service. At your current rate, you will probably pass them, bot not quite with the 1000 ft vertical separation I need. Because you are so close to fitting into my plan, asking you to expedite is the easiest - it requires the least effort from me, and I won't have to vector you around, giving you a longer than needed flight path.
If you respond with unable, I have other options to choose from, depending on the situation. Typically I would either instruct you to level off or turn. If you are descending through FL160 and I wanted you to go below someone at FL130, I would simply instruct you to level off at FL140, and then descend you further when you are clear, which would only take a few minutes. I could use the phrase "Stop descend FL140, expect further descend in 3 minutes", in which case you could adjust your vertical rate so that you reach FL140 about 3 minutes in the future, resulting in a smooth descend. Alternatively, a turn of 20-30 degrees is often enough to establish lateral separation, which then allows you to descend unrestricted. 3 or 4 minutes later, when you have passed the other traffic, you will be turned back on your track.
The key thing here is communication. As an air traffic controller, when I instruct you to do something, don't think that I don't have backup plans. We are taught to always evaluate situations thoroughly, and come up with 2-3 different solutions to every problem or situation we face. I will start by presenting the easiest solution to you, but if that doesn't work for you, please don't be afraid of informing me - I will then simply choose another solution, and adjust my plan accordingly. And remember, air traffic control is a service. We are here to make your life easier - not the other way around. You can help us doing so by communicating clearly and in due time.

I'm going to play devils advocate here and give a different perspective.
Do not say "unable", just say "N12345 Expediting". Saying unable is telling the controller that you possibly cannot descend, but in reality you are already descending in an expeditious fashion.
If the controller comes back and says "N12345 can you increase your rate of descent", then reply "unable".
From an airmanship perspective lets say you are approaching VNE in your descent but not descending fast enough (conflicting traffic or wake turbulence for example). The first thing you should do is pull the power all the way back and point the nose down. Descending with power on is probably not your best descent rate. If you are unfamiliar with how to get your aircraft low quickly, go up with an instructor and ask to practice emergency descents. I find them quite fun actually, and it has other uses (like diving through a hole in the clouds to remain VFR).

Shame protocol doesn't allow for something like "N12345 I'm expediting as fast as I can" to break the ice.

If you're already as "expedited" as you can get then letting the controller know that can be helpful (even something as informal as "N12345 expediting - can't give you much better than this though")

I'll echo everyone else and say 'unable', but I'm not even sure that's really necessary. I believe the standard definition of expedite has to be limited to the possible. If you are already at maximum safe, then you are already expediting. It should be just as valid to say 'roger' and keep flying your plane safely. I don't think he's saying 'be unsafe'; I think he's saying do it without delay.

When a controller says "expedite" they typically mean "go faster than you are now". If you hear a controller say "N12345 Please Expedite your descent" and you are already descending as fast as you can, you should reply "unable" and possibly clarify that you are descending as quickly as possible.

http://www.skybrary.aero/index.php/Urgency_Instructions_and_Clearances#The_use_of_.E2.80.9Cexpedite.E2.80.9D

Seems proper use of expedite is "do it now", not "exceed safe".

The official meaning is in the Pilot/Controller Glossary which states: "EXPEDITE− Used by ATC when prompt compliance is required to avoid the development of an imminent situation. Expedite climb/descent normally indicates to a pilot that the approximate best rate of climb/descent should be used without requiring an exceptional change in aircraft handling characteristics."

Yeah, so do it now, but don't exceed max, else you'd adversely affect handling... it's right there in your reference. It doesn't mean go faster, it means do it now. It doesn't mean be unsafe, it means do your best.

As a controller, when I instruct a pilot to expedite climb/descent, I expect them to increase their vertical rate. If they are not able to do so, I certainly expect to be told. Not saying you are unable to increase your rate further if that is the case would be extremely counter productive, and frankly bad airmanship - even if you can read the rules in a way that means you don't necessarily have to do it.

It may not be necessary, but for the sake of clarity, understanding and safety for all in the sky, it sure would be a Good Idea™

There's a reason why "I'm giving it all she's got, captain" is a Star Trek catchphrase. It provides useful information about the situation instead of just pretending a request to "expedite" is meaningless and waiting for the controller to figure it out.


text:
What does "2-2-4-niner" mean?
In Avatar (2009), a man speaks to a pilot in a jet via radio:

MAN :Valkyrie 1-6, copy...Valkyrie 1-6, you are clear for de-orbit
burn at 2-2-4-niner.
Pilot: Copy, Venture Star. Go for de-orbit burn at 2-2-4-niner.

What does "2-2-4-niner" mean?

It refers to the time 22:49 (10:49 PM). In radio phraseology, every digit of a number is generally pronounced separately, and the number 9 is pronounced as "niner" (see Why do English-speaking pilots and ATC say "Niner" instead of "Nine"?)
Often when referring to a specific time, only the number of minutes past the hour (in this case 49) are spoken, but the hour can be included as well in case there is any risk of doubt.

In US ATC all four digits are required.

@RetiredATC: check the 7110.65 2–4–17c4.

"Abbreviated time. The separate digits of the minutes only." Thanks for the correction. I always used c1. I can't even remember ever seeing c4.

Should be "Too Too Fower Niner"


text:
Who is responsible for aircraft separation in IFR (limited/no visibility)?
I was reading how-much-is-the-minimum-safe-distance-between-two-planes-in-flight and realized part of it confused me (or maybe I'm just tired.)
In a low- or no-visibility environment (i.e. under IFR rules AND conditions), who is responsible for separation of planes in flight?
§91.111 Operating near other aircraft and §91.13 Careless or reckless operation are both shown in that question/answer, but if a flight is under ATC guidance, are they (ATC) or the Pilot-In-Command (PIC) responsible?
I'm most interested in the U.S. (FAA Regs), but discussions of other regulatory bodies would be fine.

Surely it depends on whether the airspace is "controlled" or not; question should have specified this (but it's a bit late now).  Related: https://aviation.stackexchange.com/q/21888/34686 ,  https://aviation.stackexchange.com/q/79262/34686 , https://aviation.stackexchange.com/q/21888/34686 , https://aviation.stackexchange.com/q/47569/34686 , https://aviation.stackexchange.com/a/45324/34686

ATC is always responsible for IFR-IFR separation, regardless of weather conditions. That is their primary mandate, and all other services are provided on a workload-permitting basis.
In visual meteorological conditions, pilots of IFR aircraft are also responsible for seeing and avoiding other aircraft. But for IFR traffic of course this is not always possible, since the aircraft may be going in and out of the clouds.
If a loss of separation (at worst, a collision) occurs between two IFR aircraft, ATC would be held responsible (assuming the pilots followed ATC's instructions). If analysis indicates the pilots could have seen each other, they would also be held responsible.

Pilots could still be blamed if ATC gave correct instructions, but the pilots didn't follow them.

@JanHudec - Correct and decipherable. The worst airline accident in history was the result of a tower controller giving misleading radio cues to a plane requesting departure while another was taxiing on the runway

@KeithS, As far as instructions go, I would count using standard phraseology and being unambiguous as part of correctness.

@KeithS Well, the PIC of the KLM shared more responsibility I think. He was anxious, and started to takeoff without proper clearance, or proper visibility.

This is a very misleading answer. Paragraph 1: No, ATC is not responsible for separating IFR flights in airspace classes F and G. Paragraph 2: IFR pilots are not responsible for maintaining visual separation in VMC, unless instructed to do so (and they agree). Paragraph 3: We do not use "holding someone responsible" within aviation. A human error is never the cause of an incident, it is a sign of other trouble deeper in the system.

@J.Hougaard Granted about F and G and this might be worth an edit to add a footnote to that effect. You're wrong about paragraph 2. When IFR-in-VMC in controlled airspace, even though ATC provides IFR-IFR separation, FAR 91.113(b) explicitly requires pilots to see-and-avoid ("When weather conditions permit, regardless of whether an operation is conducted under instrument flight rules or visual flight rules, ..."). Your third point ("human error is never the cause of an incident") is just, with all due respect, nonsense.

@dvnrrs Before calling it nonsense, you really ought to research modern human factors, including the differences between "Safety 1" and "Safety 2". Human factors are handled quite differently in aviation compared to many other industries. The central belief is that humans do not err randomly, but human errors only happen as a result of a faulty system.

@J.Hougaard You're entitled to your opinion, even if it's nonsense. That isn't my "central belief" or that of anyone I'd climb into a cockpit with. Pinnacle 3701 comes to mind. Those guys erred, died, and were single-handedly and solely responsible for the accident. Safe pilots take direct personal responsibility for their actions and do not try to blame "human factors."

@dvnrrs Indeed, violations are a separate category of human errors which is quite unique. Here is an article that might interest you: http://www.skybrary.aero/index.php/Violation

ATC provides separation between flights depending on the airspace class in which they are flying. The following rules apply:

Class A: Separation provided between all IFR flights (VFR not allowed)
Class B: Separation provided between all flights
Class C: Separation provided between IFR flights and all other flights. No separation provided between two VFR flights. Traffic information is given to VFR flights about other VFR traffic.
Class D: Separation provided between two IFR flights, but not between IFR and VFR flights. No separation provided between VFR flights. Traffic information is provided to all flights.
Class E: Same as D, but VFR is not controlled and as such not all VFR flights are known to the controller. Traffic information given as far as practical.
Class F: Advisory service provided to IFR flights as far as practical. Traffic information provided to VFR flights as far as practical.
Class G: Traffic information provided to all flights as far as practical.

So, in airspace classes A-C, ATC provides separation for IFR flights. In D-E, separation between two IFR flights is provided, but not between VFR flights. In F and G, only advice/information is given, and it is up to the participating pilots to maintain separation based on this information, and a visual lookout.


text:
Are there US guidelines on how aviation is handled during an emergency situation?
Suppose that we find that a meteor is headed for, say, Dallas, TX, and it's too late to prevent the impact. The USA has 3 days to evacuate the area before the impact. The impact is one of the size of Tunguska: it will inflict massive damage in an area about the size of London, and we will notice the impact, but it will be mostly localized damage, so there's no global climate change or widespread damage.
Naturally, if you need to evacuate 1.26 million people in 3 days, you want to speed up the evacuation as much as possible, so you want to use all the possible methods of evacuation, be it through air, on water or on the ground, as efficient as possible.
Is there an American Federal authority like FEMA, the TSA or the FAA that has guidelines on how to handle the aviation part of such an emergency evacuation? The example of a meteorite is just that, an example. The meteor itself is not that relevant, what is relevant is how they'd handle the aviation part of the evacuation.
To clarify: I'm specifically talking about the aviation related parts, so anything related to the airspace over the area, how it would affect regional passenger traffic, to what extent local airports and pilots would be involved,... I realize there are other related actions, like evacuations through the highway and route system and through waterways and canals. Those are not what I'm interested in, insofar as they're not related to air traffic and aviation.

I don't think anyone has guidelines for that situation :-) But if someone does it would probably be FEMA, not the FAA. The FAA could provide specific ATC services and TFRs etc. but the overall plan wouldn't be their responsibility, it's just not their area of competence.

@Pondlife So this question is off-topic for this stack? Or does it still hold value if I ask about aviation guidelines in general, not specifically those from FAA? Also, I find it highly unlikely that noone has at least some manner of guidelines for a mass evacuation of an urban area.

Yes, to be serious I think someone does have those plans but I don't think it's the FAA. The security and luggage issues you mentioned are controlled by the TSA anyway, not the FAA. Right now your question seems off-topic (to me) because it's very broad but if you can make it more specific and clearly related to aviation (as opposed to ground security, for example) then it would be fine.

@Pondlife I removed irrelevant references to the ground security and the non-aviation sections and clarified that it's the aviation part I'm interested in.

Honestly, I don't think aviation would play a very big role. Highways would be the primary evacuation route, especially in a localized scenario as suggested here. This need actually arises somewhat frequently with Hurricanes. I've never heard of a significant amount of extra flights going to such areas to evacuate people. On the contrary, getting planes out of harm's way is usually a larger concern. In the case of Katrina, over 1.5 million people evacuated in Louisiana alone. In Rita, 3 million evacuated in Texas. This was almost all by road.

This question appears to be off-topic because it is about a sci-fi scenario, and not real-world aviation.

@abelenky This one is a lot more sci-fi ;-)

I think I disagree with both close reasons. How about instead of a fictional meteor, let's replace that emergency with this one: what if terrorists take over three airliners and ...

I'm pretty sure there are morw than 1.26 million in Dallas...counting Dallas proper is kind of misleading

@abelenky Urban evacuation isn't a sci-fi scenario. It happens every few years, at least. Sometimes more than once in the same year, such as 2005. It also often results in evacuating a population larger than that of Dallas. Most of the answer is off-topic, though, because the answer is basically "aviation doesn't do much of anything except get planes out of harm's way while everyone evacuates via highway."

Given the scenario described, this is highly speculative but I'll have a go anyway.
I assume that FEMA would be responsible for the overall evacuation and indeed their transportation annex says that the FAA's main responsibility in an emergency is limited to airspace management:

DOT/Federal Aviation Administration (FAA) is responsible for the
  operation and regulation of the  U.S. National Airspace System,
  including during emergencies.

The same document appears to rule out military control of US airspace (my emphasis):

Under certain conditions, DOT/FAA may delegate  use of specified
  airspace for national defense, homeland security, law enforcement, and
  response (e.g., search and rescue) missions, but retains control of
  the airspace at all times.  DOT/FAA may also implement air traffic and
  airspace management measures such as  temporary flight restrictions in
  conjunction with these missions.

In practice, the main thing the FAA would do is to set up one or more (possibly very large) Temporary Flight Restrictions to ensure that only emergency and evacuation aircraft could use the airspace around the affected area (see 14 CFR 91.137). In the catastrophic scenario you described, it might be serious enough for the FAA to close the entire national airspace system to non-emergency traffic - as they did on 9/11 - because the refugees would presumably have to be taken all over the US and the evacuation would be a genuinely national crisis.
Apart from that, the FAA could provide extra ATC services by calling in controllers from vacation and/or making them work overtime; they would probably also have to implement some quick procedures to manage the increased air traffic in the area. They could waive or suspend rules on crew working hours, required aircraft maintenance or anything else that would reduce the amount of time that evacuation aircraft could spend in the air. Of course all these things would increase the risks involved in operating the aircraft, but in the face of an unavoidable disaster that would presumably be acceptable. Anyway, I guess no one would prosecute a pilot for flying overtime to save lives in such an extreme situation.
Mobilizing GA aircraft for the evacuation is another possibility (an aviation equivalent of the Dunkirk evacuation) and the FAA could help there by setting up temporary ATC procedures, creating ad hoc control towers at smaller airports and so on.
The FEMA document linked above implies at least some planning has been done with the FAA on disaster response:

DOT/FAA Response Cells: FAA activates specialized response cells to
  manage and  coordinate air navigation services and other
  aviation-related efforts.

But what FEMA and the FAA would really do in a specific situation is very speculative and has much more to do with disaster response than aviation: the aircraft are just there to move people and things around, and the real challenge is deciding how to use them.


text:
Why does the ATIS say "read back all instructions"?
Whenever I'm at a class D, I'm always confused as to why the ATIS says "read back all runway assignments and hold short instructions." Isn't that just a given? It seems redundant and it takes up valuable time in the ATIS broadcast. If I tune in half way through the reading, I don't want to have to sit there for 5 minutes just to hear the whole thing.

Where does the 5 minutes come from? The redundant bit takes 5 second max to read.

Because the lawyers say we have to, reference the 7110.65 2–9–3o. Why they say that I'm not sure but I can guess because of historical runway incursion incidents.

@ymb1 Au Contraire!  KMCI has "migratory waterfowl" ever-present in the vicinity of the airport, rather than mere "birds" (at least per their ATIS). Still haven't figured out how one should do things differently in the case of the one or the other, but maybe some day...  (For that matter, what can one do differently in the rare but hypothetically possible case of flying into an airport with NO birds, migratory water fowl or otherwise, in the surrounding land, seas, or skies???)

@ralph j Are there birds at NZSP? At least the kind that fly?

Due to the ongoing runway incursion epidemic, US ATC must hear every aircraft read back certain instructions, including callsign. If you don’t read them back correctly, they’re required to repeat the instruction until you do. No matter how many times it takes.
When this rule was first adopted (or at least enforced), a shocking number of pilots couldn’t give proper readbacks. This caused a lot of frequency congestion and other issues, such as making an aircraft on final go around or holding departures just because someone taxiing toward that runway wouldn’t properly confirm they’d hold short of it.
Things have gotten somewhat better as pilots have learned, but it is still common enough of an issue in practice that they won’t take the reminder off the ATIS. And since some other countries either don’t have or don’t enforce this rule, it may never go away.

Analysis of Runway Incursion Data - NASA, NTSB Fact Sheet, FAA Runway Incursions, Transport Canada Final Report, EuroControl Action Plan

And FAA Runway incursion Database). Just cherry-picking #s - 1999: 321 (4.7/M ops), 2007: 371 (6.07/M ops), 2019: 883

Failure to readback runway assignments and hold short instructions is still a common occurrence.  Enough so that the brief moments taken by including the reminder on ATIS are nothing, when compared to the time taken to query pilots, and make second transmissions, to elicit the necessary information.
It only takes one error (did he say hold short, the left, or right runway?) or one missed clearance, or one missed hold short instruction, to lead to a runway incursion or mishap.
The announcement is made at so many locations on ATIS because it's a widespread, ongoing problem, and has been, for many years.

This procedural requirement is not established by Federal Regulation (FAR) but is specified in the Aeronautical Information Manual (AIM). After getting their pilot's license a surprising number of pilots forget the AIM exists, and eventually forget that the procedural requirement (and hundreds like it) exists. Therefore the reminder in the ATIS.
AIM Chapter 4 - Air Traffic Control, Section 3 - Airport Operations, Paragraph 18 - Taxiing…

(a) General… (9). When taxi instructions are received from the
controller, pilots should always read back: (a). The runway
assignment. (b). Any clearance to enter a specific runway. (c). Any
instruction to hold short of a specific runway or line up and wait.
(10). Controllers are required to request a readback of runway hold
short assignment when it is not received from the pilot/vehicle.
Since a landing clearance may include a Land And Hold Short Operation
(LAHSO) that is similar to 9(c) above, further read-back guidance is
provided…

AIM Chapter 4 - Air Traffic Control, Section 3 - Airport Operations, Paragraph 11 - Pilot Responsibilities When Conducting Land and Hold Short Operations (LAHSO)…

(b)… (7). Controllers need a full read back of all LAHSO clearances.
Pilots should read back their LAHSO clearance and include the words,
“HOLD SHORT OF (RUNWAY/TAXIWAY/OR POINT)” in their acknowledgment of
all LAHSO clearances. In order to reduce frequency congestion, pilots
are encouraged to read back the LAHSO clearance without prompting.
Don't make the controller have to ask for a read back!


text:
Can instruments be fixed via a swift punch?
I remember reading a book about private piloting techniques, (I can't remember the title; it has been so long; perhaps I can check my library history or something to see later), and I saw something bizarre.
The author was discussing instruments, and what to do in case of failures. He wrote something about how, in the case of a failure of a critical instrument, in a situation where you really need it, that one should punch out (or otherwise destroy) the glass of the gauge, to allow air into the system.
What?
Is there any way something like this could be useful, or at least theoretically logical? Can anyone deduce any sense out of this?

Ah, the old percussive maintenance.

Yes, it's a thing, but many airplanes today have an alternate static source that can be switched on instead...

Once while I was flying a C172 or PA28 there was a gauge I was suspicious of the reading. When I tapped the face of the gauge with my fingers a couple times, the needle set itself to about where I thought it should be. I believe it was the oil pressure gauge and after the tap it matched the (illuminated) low oil pressure annunciator.

Low oil pressure? Not good!

If the static port gets blocked in an aircraft with no alternate static port, you can break the glass of the VSI (Vertical Speed Indicator) to allow air from inside the cockpit in the static system. By doing this you will sacrifice the VSI in favour of the altimeter and airspeed indicator
Due to venturi effects, air inside the cockpit has usually a slightly lower pressure than the pressure measured by the static port outside your aircraft.
This causes your altimeter to indicate a higher altitude and the airspeed indicator will also indicate a greater speed. The VSI is useless after you break it.
Needless to say this does not apply to pressurized cabins nor to glass cockpits...

This works because the inside of the VSI contains a diaphragm in a pressure chamber. The diaphragm is connected to the static system through an unrestricted tube. The chamber is connected to the static system through a  restricted (calibrated) leak. If the static pressure changes, the pressure in the diaphragm  changes instantly, while the chamber pressure lags slightly behind. This causes the membrane to expand / retract which drives the needle on the instrument.
When the glass is broken, the chamber will be at the same pressure as the cockpit. Through the calibrated leak, the static system will be levelled with the cockpit pressure, but of course with a delay as well. The VSI will now work in opposite direction (if you didn't destroy the needle).

The inner workings of an IVSI
Some VSI apparently have the calibrated leak into the cockpit already. For such VSI's smashing the glass does not work. Here the diaphragm should be destroyed as well.

As the old adage goes, those in glass cockpits shouldn't thrown punches.

I wonder how many people would be able to work out if it was a dynamic or static problem they were facing?

@Simon: A blocked static port will cause the indicated altitude to freeze at what the altitude was when the port was blocked; a blocked pitot tube won't affect the altimeter.

The FAA Instrument Pilot Handbook (11-8) mentions this as an alternate source if you lose your static source (not vacuum).
That said, I don't think every VSI is identical.  I have seen arguments that some are not vented the same way and may not provide a valid static source.

Ach, thank you for clarifying that this is NOT for vacuum, but static.

authors: ชนะชัย จันทร์สด


text:
Intercepts and aerial combat in IMC (or my no-fly zone is full of clouds?!)
If a reasonably modern fighter was placed into a situation where they had to engage in aerial combat while in IMC (say if radar picked up non-squawking aircraft coming from a hostile military airbase toward a no-fly zone that you're patrolling, and said no-fly zone and its immediate vicinity are full of clouds), could it be done?  What techniques would be used?  Or would the fighters seek to meet each other away from the cloud cover, since aerobatic maneuvering in IMC is generally not a good idea?
Furthermore, if it was an unknown (not necessarily known-hostile) aircraft incoming, could it be intercepted in IMC, or would the intercept have to wait until the unknown aircraft emerged into VMC?

If the fighter has radar SA to the offending aircraft, it can very easily affect a radar interception and close to within up to .1NM of the bogey if a visual ID and escort are required.
Otherwise, if a facility, such as an air intercept controller, has already deemed the aircraft to be hostile then the fighter will engage the aircraft as appropriate through the use of radar guided munitions.
In situations where an aircraft is already known to be hostile, BVR engagements will likely be the initial engagement choice anyway, and, in this case, it doesn't matter what the weather conditions are because the fighter is running an entire engagement based on his radar and will remain outside the visual arena anyway.

In the first scenario, where it sounds like you're assuming that the intruder aircraft is known to be hostile even without seeing it, a shot with a radar missile would be unaffected by the IMC, and that scenario is a pretty straight-forward kill.
The hard part of IMC for a modern fighter aircraft isn't killing the target, it's getting the positive ID on it that's necessary before shooting in order to assure the chain of command that you aren't, in fact, about to kill a neutral or friendly aircraft who's wandered into the wrong place at the wrong time with the wrong squawk.  THAT is where VMC becomes necessary, in most cases, to get the required visual ID on the target.
Using radar alone, an interceptor could close to some reasonably short distance (say, inside a mile, with some altitude separation as well), and if the unknown aircraft enters VMC even briefly, then the intercept could be completed to the point where one interceptor makes the visual ID.  With the aircraft being known to be hostile, that interceptor could break away, and a wingman, maintaining position further back, could then take the shot with a radar missile.
Presumably, the "bad guy" has some mission to complete, and most of those (though not all) tend to need VMC to accomplish -- dropping bombs or taking photos or whatever.  So chances are probably pretty good that the intruder is going to get to VMC eventually.  (Or, if he drops bombs off of radar/GPS, then that act itself might be sufficient confirmation of hostile intent that the interceptors would be cleared to engage, ensuring that the bandit doesn't live to ever repeat that mission.)

In most no-fly zone situations in recent memory, the mission the pilot violating the zone is most often sent on is martyrdom, more or less trying to get shot down just outside the NFZ so his country can claim a violation of the cease-fire and try to rally their forces.


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What's the north boundary of the KINS Class D? (Or: does a SUA designation take precedence over controlled airspace?)
This is inspired by the question regarding aerobatics over a surface class D area.
KINS (Creech AFB) sits right outside the south boundary of the Nellis Range Complex (R4806W to be precise).  Considering this, and considering that it has surface Class D around it whenever the tower's open as per the A/FD...does that class D airspace abruptly end where R4806W begins just north of the airbase, or does it continue all the way around, leaving a portion of airspace that's both a Class D (sfc) area and SUA (i.e. restricted airspace)?

According to the sectional chart, Class D airspace does not extend into the restricted area.

SkyVector KINS Sectional Chart
The restricted airspace starts at the surface to an unlimited altitude.  According the JO 7400_11A.pdf, Class D does not enter the restricted area.

Class E airspace is the same.

The sectional chart does display it that way -- but I'm not sure if that reflects the actual airspace boundaries, is a charting limitation, or if something else is going on (note that the vignette doesn't extend along SUA boundary)

Vignette?  Are you talking about Class E airspace starting at 700' AGL.  If so, it stops where the restricted area begins leading credence to Class D also stopping where the restricted area begins.

Ah -- I got the vignette and the dashed line mixed up -- but you'd think they'd draw a dashed line (and/or vignette) parallel to the SUA boundary if the Class D and E airspaces ended at the SUA boundary, no?

Page 377 of the linked to document contains the information you are looking for.  It is regulatory in nature as it is referenced in §71.61.

That's exactly what I'm after, thanks!


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What would non-potable water be used for on an airliner?
Airliners have potable water tanks and distribution systems for galley functions and such; of course, this water is used for any non-potable functions as well as it's what's available on a modern airliner.
However, this question makes me wonder if there are water uses on an airliner that could be served by a separate non-potable water system, or if all the water needed is potable.  If there are non-potable water uses, what would they be?

Potable water systems need special requirements to contain drinkable water. They need to be periodically sterilized, piping, etc. It is actually a lot easier to consider all water onboard non-potable and just have people drink bottled water or use bottled water for things like coffee.

Maybe interesting: this video by Captain Joe explains parts of an aircraft's water system.

Aircraft travel in countries were pathogen bacteria or viruses are carried by insects which like to lay their eggs in stagnant water. Aircraft water systems must be designed carefully to prevent spreading diseases.
On a typical airliner like the Boeing 737NG, you won't find any non-potable water source that would contain chemically untreated water. Equipment is fed from the potable water tank. Used water is either dumped overboard or stored. From the aircraft familiarization manual, the water system:

and the toilet waste system:

Condensation water is a by-product of many systems cooling air (including by expanding it). This water is collected and drained overboard. Jet engines (including APU) are the main generators of water, as fuel combustion generates essentially water (in mass) and CO2.
It's worth noting that at cruise altitude, moisture in atmosphere can be insufficient for humans well-being. The water extractors present in air-conditioning packs then reincorporates a part of extracted water into conditioned air.

Non-potable water = undrinkable. Lavatory facilities such as toilets and sinks, and showers such as in the Emirates A380s could be a use of non-potable water on aircraft. That said, why complicate the matter by having two separate water systems? Plus, dirty water would clog up pipes and build up deposits... so why use it?
Now if we're talking about aircraft that DO use non-potable water then look no further than fire fighting aircraft that pick up water from lakes and rivers and dump it on wildfires.

The water that goes down the drain has to go somewhere. I'm not sure if they separate it out, but stuff from sinks/showers may go into a grey water tank and the stuff from the toilets would go in a black water tank.

@RonBeyer it's stored in waste tanks which get emptied after landing and either dumped or sent to a waste water processing facility (depending on the laws and available facilities in effect)..

It's not just complication, aircraft are plenty complicated :) Main problem is weight (and to a degree size). Adding the extra tanks and piping (plus the valves, access hatches, etc. etc.) would add a lot of dead weight to the aircraft, meaning less cargo/passenger capacity and/or reduced range. Operating cost goes up, fuel burn goes up, which in turn means even higher operating cost (and environmental impact). Far more effective to use the same water for all operations.

If I were an aircraft designer, I would most definitely not supply non-potable water to the sinks & showers. That would be a lawsuit waiting to happen should someone contract something from drinking from either. I would simply assume that someone would.

@FreeMan I agree - both a waste of weight and a lawsuit waiting to happen. I did say "could" and the question was asking for hypotheticals. I suppose the real question ought to be "would the Russians do it?" :-)

The water source needs to be checked. When I worked in LH it was done twice a year. It was a chore because we had to arrange an airport-pass for the lab guy as he need to get a sample from the spot where they got the water, as well as samples from two of the trucks. Once the test has been passed we were good for another 6 months. Actually the validity was for 12 months but the test was done every six to avoid any gaps, due to late lab reports, station overlooking etc. A list of stations where water uplift was allowed was published on a page in our computer system. If the airplane was inadvertently filled with water from an untested source FRA ops needed to be advised ASAP as the airplane water system would need to be cleaned/flushed before the next sector.
At one point we stopped pax flights and only flew freighters, at this time the requirement for water uplift stopped as freighters did not need so much water. As such we stopped the water checks and KUL was taken off the approved water uplift list. If I'm not mistaken the 74F took on around 400kgs, The MD11 around 250kgs.
One day we had an MD11F come in with almost zero water uplift and the Captain wanted water. After some discussion we uplifted about two crates of large Evian bottles.


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Could you ever legally authorize yourself to fly an aircraft that would require an LOA, based on your other certs?
The question about being certified to fly aircraft that don't fall under a type rating got me thinking. For all knowledge possessed by humans there must be a source. If you want to get certified on a Bombardier CRJ narrow-body, you have to be trained by someone who has not only also been rated to fly it, but certified to train on it.
This process is inherently iterative; someone trained your trainer, and someone else trained your trainer's trainer, and so on until at least a time when there were no aircraft of that specific model. At some point, someone got their approval to fly and teach that model without a single hour of stick time in that specific model of aircraft, because it simply didn't exist.
For aircraft like a Bombardier, the alternate training avenues are obvious; the manufacturer, located in a staunch U.S.-allied nation, will produce training materials and at least fixed cockpit sims, which when coupled with flight time in some other narrow-body T-tail jet, will serve as the basis for certification to fly and ultimately train others on any new Bombardier model. However, this gets tricky when you consider models of aircraft not falling into FAA-defined types, especially single-seaters, and definitely the first one or two of these aircraft to enter civilian hands. Vintage ex-mil planes, especially from non-Allied countries, are the primary example; how did the first civilian Zero owner get certified to fly it?
One possibility I thought of for how this could come about is based on the fact that there are a number of pilots/instructors with an extraordinary number of ratings. The current record, IIRC, is over 100 type ratings and/or specific aircraft model certifications. At some point, more training for a pilot like this on any specific airframe becomes redundant; there's nothing the pilot can learn from a CFI that a combination of the pilot's own experience on comparable models and whatever training materials exist for the airframe could provide. A pilot like this would be an obvious choice to take the first flight in some new plane, unique in the U.S. civvie world, but technically he'd still need authorization to do so.
So the question is, is there ever a "tipping point" where a pilot can legally use some combination of his existing qualifications to assert by himself that he has the required knowledge and skill to fly a first-of-its-model plane, for which he does not have an LOA and could not get one through normal channels?
One possible example. Say it's 1992. The Soviet Union has just broken up and the Red Army's military hardware is being auctioned off to the highest bidder. A collector and flight enthusiast in the U.S., who already owns and flies some ex-mil jets like the F-86 Sabre, heads overseas and buys himself an old MiG-17 from the USSR reserve forces in flyable condition; the first one ever to be in private American hands.
Now, how does he get certified to fly it within FAA-controlled airspace? Does he have to find a former Soviet pilot who can train him, and somehow transfer that Soviet pilot's voucher into an FAA LOA? Is there some high level of instructor certification that allows a CFI to train on airframes the CFI himself is seeing for the first time?
Or, can the collector himself, given his existing LOAs for closely comparable aircraft including his own Sabre, assert that he is capable of flying the MiG-17 and do so without anyone else having to vouch for that ability?
The only thing I can think of besides the pilot just saying "someone's gotta be the first to learn to fly this thing, and it might as well be me", is for the FAA to say exactly the same thing, and directly issue some sort of special provisional authorization for the collector to learn the aircraft for himself, hands-on, no CFI. This authorization would naturally contain all sorts of restrictions on when/where he could fly it (if I were the FAA watching someone learn to fly a military jet, I'd point him to the nearest MOA), until he could somehow demonstrate to someone that he'd attained mastery of the airframe and have most or all of the restrictions lifted with an LOA. The specifics of how all this would happen, though, escape me.

I like this question! It is a nice thinking experiment! +1!

These pilots are called test pilots. They attend a test pilot school and then can legally fly a new aircraft.

Read this http://www.avweb.com/news/profiles/182142-1.html

The answer to this, at least for planes that sport big, whirly props, lies next door to the FSIMS, in FAA Order 8900.2, the "General Aviation Airman Designee Handbook".
Specifically, you'd contact your local CAF wing or the EAA Warbirds division, who'd then put you in touch with an appropriately qualified National Designated Pilot Examiner (NDPE) via the National Designated Pilot Examiner Registry, or NDPER -- between them, you can get checked out on any reciprocating aircraft, even a Zero, a Bf-109, an Il-2, or a Mosquito.
Non-type-certificated turbojet aircraft follow the 8900.1 checkout procedures -- a temporary LOA would be issued as Lnafziger pointed out, usually with an EPE (Experimental Pilot Examiner) or NDPE (yes, some of the NDPEs can check you out in jets too) giving you the final "checkride", based on their qualification in similar types of aircraft (for instance, if you hauled a Su-30MK home from the Sukhoi factory, you'd probably have an ex-F-15 pilot or the likes checking you out on the type).
Of course, if it's a UFO (aka something that is not of any extant category or class), then AFS-800 would probably have to step in and send or designate someone.

The original question which you linked to contains a link to the FAA Inspectors Handbook, which covers this scenario as well:

5-1590    TEMPORARY LETTERS OF AUTHORIZATION.
A.    For one‑of‑a kind aircraft, first‑of‑a‑type aircraft,
  amateur‑built aircraft, practice in a single‑place aircraft, or other
  special cases, a temporary LOA may be issued. Temporary LOAs may only be issued for a
  specific purpose and should be for a specified, limited duration. ASIs
  who receive requests for temporary LOAs for operating experimental
  aircraft must coordinate with the NPO before issuing them. These LOAs
  may be required to ensure compliance with the aircraft operating
  limitations.
B.    Temporary LOAs for the operation of experimental aircraft should
  not be confused with temporary LOAs for the operation of TC’d
  aircraft. Section 61.31(b) permits operating TC’d aircraft under
  limited circumstances. These LOAs are issued in accordance with the
  guidance in Volume 5, Chapter 9, Section 3.

Mark Clark, the owner of Courtesy Aircraft, has the following pilot certificate, which allows him to fly anything.

Well, almost anything -- you'll note that this doesn't extend to a full set of type ratings for jets.

only pistons??? uh, he's such poser!

granted, he does have some jet qualifications (T-33, CE-T37, CM-170)

That's all piston aircraft, not all aircraft.


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Chocks - why the wide variances in price?
In a comment to a question about setting the parking brake, @rbp said to just get a set of wheel chocks and use those instead. I was piqued - it never occurred to me you'd need your own, I thought they'd be littered around the tarmac for common use - and did a quick Google Shopping search for "aircraft chocks". I was surprised to see a wide price variance, even within a subset of relatively small-size chocks.
For instance, here is a pair of 10" rubber chocks with 3ft rope, about 15 lbs, for \$15. Here is what looks like exactly the same thing, for \$98. Tigerchocks make considerably lighter ones, but they are \$120-ish per chock (over \$200 for any roped pair) while other lightweight designs are as cheap as \$30 for about the same size. Other designs seem to vary between $20-60 for a roped pair, and have noticeable differences in size and design, but c'mon, they're a wedge you put under the tire to stop the plane rolling.
How much of this variance is "you get what you pay for" (more money equals a better product in some way; lighter, grippier, more durable etc) and how much of this is "caveat emptor" (the aviation crowd are used to paying a lot for their gear, so some yahoo with an MBA says "let's see how much we can milk them for a pair of rubber blocks tied with a rope")?

The point of wheel chocks is to prevent the tire from rolling (and thus the aircraft from winding up "somewhere other than where we parked it). The aircraft doesn't know how much we spent on the chocks, and if it did it probably wouldn't care. (OK, it might laugh at you if you buy solid gold bars to chock a Cessna 150.)
Aside from pretty obvious quality-related things (a $5 set of chocks made out of cheap rubber that fall apart when you squeeze them in your hand)
the big reasons for price differences come down to a few things:

Size
Just like with chocking a car or truck there are various sizes of chocks available, and they vary in length and height:

For very large aircraft very large chocks are used (wider and taller):

…and for smaller aircraft smaller chocks are used (shorter and narrower):

Big chocks require more material, and thus cost more to make than small chocks, so logically they cost more.

Nice Features & Laziness
I have a set of $20 aluminum wheel chocks. They have a bungee cord that keeps them tight against the tire (so there's no room for the tire to roll), and they weigh just over 1 pound (they're light and small enough to throw in the plane without thinking about it).
The guy two planes down from me has a wheel chock made of three sections of 2-by-4 inch lumber, screwed together to be just slightly wider than his tires and painted safety-orange. It probably weighs less than 5 pounds and cost him $10 and a few minutes with a power drill & spraypaint.
Both work equally well, but I was willing to pay for someone else to cut and bend some aluminum that I can fold up into a small space easily rather than finding a chunk of lumber I didn't need and making my own chock.

"Standard Aviation Markup"
There's a joke that when trying to determine the price of a component for an aircraft you take the price of that component in a non-aviation application and add some zeros to the end of it.
That's not a joke in this case: Those two rubber chocks you posted are, for all practical purposes, identical - with the exception of their price.

Good answer as always. I was going to ask about the feasibility of homemade chocks; didn't know what kinds of FAA or ASTM ratings might be required of something like this that might justify the cost, when you could make practically the same thing out of an old fence post with a chop saw.

@KeithS the basic criteria I personally have for chocks are that they be at least as wide as the tire (preferably a little wider), and "tall enough that you can't roll over them". The latter is important for those nice light aluminum chocks (if you roll over a bent angle of aluminum you may well squish it flat - or at least flat enough that it's a less effective chock and you can roll over it easier next time).

It's probably worth pointing out that the military chocks shown here are just wood (a length of nominal 4x4 or 6x6, depending on the wheel size, with a chamfer) and rope. They're used for short-term use on the tarmac and inside hangars; much more substantial metal chocks are used for longer periods outdoors.

@StanRogers Yeah, I couldn't find any other good pictures of "large airplane" chocks that weren't all watermarked & hard to see what was going on. The main point is to show that the chock blocks the entire face of the whee/truck (as opposed to just being a little pebble that the tire can roll over)


text:
How does Chicago O'Hare's tower sequence aircraft at peak capacity?
This older question asks at what interval planes take off and land from ORD. The accepted answer (one takeoff or landing every 30-40 seconds) jives with my math: 2416 operations a day on average, with winds in a non-cardinal direction all those flights must use just two runways, so worst-case each runway would have a plane rolling along it every 75 seconds round the clock (so a plane takes off or lands from somewhere in the airport every 37.5 seconds).
My question is, how? At that rate, approaching planes would be spaced a scant two and a half minutes apart, and as soon as a landing plane passed over the numbers, a departing plane would be told to line up, then to take off as soon as the landing plane had cleared the runway, and if they hesitate even a few seconds the plane behind them would have to go around. How is this traffic density maintained long-term, especially since, like any airport, it has peak periods of activity exceeding the average?
Follow-up question; is ORD as bad as it gets, or are there "denser" airports with lower total aircraft movements but fewer runways? I heard Heathrow is so bad its airspace is ICAO Class A, prohibiting VFR flights entirely, in part due to the fact the airport handles practically every international flight into London on just two runways.

According to the FAA, AirVenture gets mighty close this time of year.

Not too bad; "over 10,000 planes" visiting a Delta-size airport with only one usable runway in any given wind direction over a period of 7 days. Assuming they're all flown to the airport, stay on the ground for the event, then fly out in a perfectly spaced schedule 24/7 through those 7 days, the runway would see an aircraft every 30 seconds. What's even more likely is that a majority of those aircraft add another TO/L for at least one demo flight, further increasing traffic.

They have 2 North/South runways - they convert a taxiway into a runway!  See the notam (pdf) around page 13 or so

Very cool. Looks like they also use 9/27 concurrently, so they have three active runways in calm winds. Still a nightmare; approaches to runways 18L and R require staying above 1500'AGL until they pass 9/27, making for a pretty steep glide slope. They also can't use 36R (the converted taxiway) for departures as departing from 36L requires a serious cut to the right to avoid departing traffic on runway 9.

Chicago runs simultaneous triple parallel approaches. And as soon as an aircraft clears the runway, another one is allowed to cross the threshold.
Chicago Tower actually does not do the bulk of the sequencing of aircraft. Chicago TRACON actually sequences the aircraft before they are handed to the Tower. Even before that, Chicago ARTCC begins to sequence inbound aircraft. Similarly, aircraft are handed to departure (TRACON) almost immediately after taking off. Departure procedures are optimized for safety and efficiency.
This figure breaks down runway usage percentage for arrivals and departures in April 2015 (7am - 10pm traffic)(source paper). It highlights the common westbound landing flow with triple parallel runways. You can also see two diverging runways used for the bulk of departures, with sporadic usage of others.

Note that this is all after an airport runway overhaul. Consider that 2014 saw almost a 10% decrease in operations from the year 2005. Having talked to controllers that have put in time at Chicago Tower, it is as crazy to handle as humanly possible.

Nice. I notice the southern E/W runway is labelled 10/28C. Are there plans for 10/28R south of the cargo complex?

Indeed, see the diagram in another question.

Amazing answer.  I was also wondering, as the OP asked "is ORD as bad as it gets, or are there [even] "denser" airports with lower total aircraft movements but fewer runways" .. ???


text:
What is the area between the taxiway and runway shown in the picture below?

Is this the Arresting area? I'm not too sure what you call this area

I feel like I've seen a similar (potentially duplicate) question in the last year or so...

Is this an Air Force base?

Which airport is this?

Additional information on the airport would have been nice, but from the markings it looks like it simply is a pad where two aircraft can be positioned at once.
This can be useful where you have a case of eg. one aircraft needing additional time to be ready for take-off while the aircraft behind is all set, or a larger aircraft in front being held back to allow a smaller aircraft to pass it and take off first.
Copenhagen Airport (CPH) has a similar layout at the end of one of the runways, as shown below, although this is using two taxiway stubs rather than one solid pad.

I suppose it is a turning area for making a U-turn after a backtrack. You can see traces from such turns on ground

I thought so too, but why would they backtrack when there's a taxiway?

@PerlDuck sometimes taxiways are unusable for one reason or another.

I bet the runway was extended and a turnaround pad was added before the taxiway was built or extended.

If this is a military airfield it is the arming area where ground crews do final arming of ordnance on the aircraft before it takes off.  The extra space also allows more room for marshalling multiple mission aircraft to compress takeoff intervals.

and if civilian it may be a deicing pad.


text:
What is P-RNAV?
I came across the term P-RNAV.
What is P RNAV, and what are the differences from 'standard' Area Navigation(RNAV)? Is there a specific set of requirements for P RNAV?

Hello Kim Kim, welcome to aviation.stackexchange.com! I have rephrased your question a bit, so that it may attract more focused answers. Please feel free to update and expand further.

https://www.skybrary.aero/index.php/Precision-Area_Navigation_(P-RNAV)


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What's it like to be a volunteer at the temporary airport set up at Burning Man?
I've heard that the Burning Man festival sets up a temporary airport each year for the week of the festival and that it is staffed by volunteers.  What is it like to be a volunteer there?  Do the employees at surrounding airports find dealing with them better or worse than non-volunteer airports?
Update: Previously I asked what it is like to be a "volunteer ATC", but that is not the right terminology. I have broadened the question to be less specific.

Black Rock City airport (88NV) has a website, such that it is. (http://www.portofentry.org) It appears that during the Burning Man festival, the airport has a Unicom operator, but there is no "ATC" as such. It's a non-towered strip. Any ATC would come from Reno, or whatever part of US ATC controls that airspace.

Thanks for the details.  What's a "Unicorn operator"?

@tom unicOM, not unicoRN. I admit, that's how i read it the first time, too.

d'oh!  The font really looks like an "r n" not "rm". (I guess it's the Stack Exchange unicorn mascot influence!)

you en eye see oh em, u n i c o m. Radio.

In Tom's defense, he has been working at Stack long enough to be corrupted by the unicoRN memes... also the kerning in the default font is pretty awful sometimes.

I volunteered at the Airport in 2015 and it was a really cool experience.
I only worked one shift as "Night Watch" / "Border Control" which is basically making sure people going to/from the event to the parked airplanes have the proper wristbands and making sure no one tries to sneak in at night. There are a ton of other positions listed on the volunteer website you can read about here: http://airport.burningman.org/us-who-we-are-and-were/volunteer-info/
The volunteer jobs range from logistical stuff like processing passengers, to ramp operations like guiding taxiing traffic, checking arrival documents to actually running the UNICOM and giving weather advisories to local traffic, particularly about what runway/pattern is in use given the current winds.
Many of the positions (especially ramp side jobs) require some familiarity with how the airport operates and my impression was you "worked your way" up to those. Like many things at Burning Man, if you show up, volunteer and contribute you can end up doing some cool stuff.
You can subscribe to the volunteer mailing list by sending a blank email here:
airport-announce+subscribe@burningman.org
If you're curious about pilot experiences flying to/from the event (which is what I think your original question was about) I would subscribe to the aviators discussion list by sending a blank email to this address: aviators-list+subscribe@burningman.org
Both are great resources for getting first hand information about what its like to fly into and volunteer at 88NV

From the website that CGCampbell links to in his comment, it can also be found that the airport is located in Class G airspace. Class G is uncontrolled (see and avoid) airspace, so there is no air traffic control active in the airspace around the airport.
It also says flight following may be requested from Reno:

The controllers in Reno are familiar with our location, and it’s OK to give them Burning Man or Black Rock City as your destination when requesting Flight Following. However, if you’re lower than 10,000 feet they will most likely end radar services with you around Pyramid Lake. Close your flight plan prior to losing contact.